Newsom had signaled the move in his State of the State address in February but made it official Thursday by asking state agencies to withdraw existing permits for the project and start over with plans for a single tunnel

"I do not support the twin tunnels," Newsom, a former lieutenant governor and San Francisco mayor, has said. "But we can build on the important work that's already been done."

California has already spent $240 million developing the project, according to state Department of Water Resources Director Karla Nemeth. She told The Associated Press that some of that work will inform the new approach.

Brown's plan called for the construction of two 35-mile-long tunnels to divert water from the Sacramento River, the state's largest river, to the San Francisco Bay Area, San Joaquin Valley and Southern California. Local water agencies were expected to foot the roughly $16 billion bill, but many of them balked at picking up the tab.

The plan had been downsized to a single tunnel in early 2018 before the Metropolitan Water District of Southern California, the state's largest water agency, agreed to cover nearly $11 billion in costs last April, bringing new life to the project.